Communications apparatus and communications system using multicarrier transmission mode

ABSTRACT

A base station accommodated in a communications system for communicating with a mobile station, the base station includes: a transmitter configured to generate frequency band information indicating which frequency band of frequency bands used in the communications system to communicate with a mobile station, to transmit the frequency band information by using a specific frequency band selected from a plurality of frequency bands available in the system, and to communicate with the mobile station using at least one of the plurality of frequency bands.

CROSS REFERENCE TO RELATED APPLICATION

The present application is a continuation of U.S. application Ser. No.14/667,258, filed Mar. 24, 2015, now pending, which is a continuation ofU.S. application Ser. No. 14/175,564, filed Feb. 7, 2014, now U.S. Pat.No. 9,036,593, issued May 19, 2015, which is a continuation of U.S.application Ser. No. 13/555,767, filed Jul. 23, 2012, now U.S. Pat. No.8,705,479, issued Apr. 22, 2014, which is a continuation of U.S.application Ser. No. 12/607,570, filed on Oct. 28, 2009, now U.S. Pat.No. 8,363,610, issued on Jan. 29, 2013, which is a continuation of U.S.application Ser. No. 11/790,789, filed on Apr. 27, 2007, now U.S. Pat.No. 7,953,167, issued on May 31, 2011, which is a continuation ofInternational Application No. PCT/JP2004/016154, filed on Oct. 29, 2004,the contents of each are herein wholly incorporated by reference.

TECHNICAL FIELD

The present invention relates to a communications system for exchange ofinformation (data) between communications apparatuses by a multicarriertransmission mode by a series of subcarriers, more particularly relatesto a communications apparatus accommodated in that communicationssystem.

BACKGROUND ART

A most preferred example of the above communications system discussed inthe present invention is a mobile communications system. The followingexplanation will be made by taking as an example this mobilecommunications system. Accordingly, if according to this example, thecommunications apparatus is a (i) base station (or a higher base stationcontroller thereof) and/or a (ii) mobile station (including a mobileterminal such as a PDA). Note that for convenience, in the laterexplanation, the former (i) will be referred to as the “base station”and the latter (ii) will be simply referred to as the “terminal” in somecases. Note that, as will be clear in the later explanation, the presentinvention can be substantially equivalently applied to not only theabove base station, but also the above terminal. It is not particularlynecessary to differentiate between the two.

In a mobile communications system, securing a desired transmission ratefor a user is a major issue in providing it with service. On the otherhand, usually the used frequency band used by the mobile communicationssystem is fixed for each system. Therefore, even if employing usermultiplexing etc., the maximum transmission rate thereof ends up beingrestricted. For this reason, the method of flexibly changing the usedfrequency band in accordance with the required transmission rate isbeing studied.

Further, when considered by the mobile communications system as a whole,the state of usage differs for each used frequency band. Sometimes aband is not used at all. For this reason, from the viewpoint of theeffective utilization of the frequency, it has been studied to make theused frequency band variable.

Under this situation, technology of making the used frequency bandvariable in an MC (Multi-Carrier)-CDMA (Code Division Multiple Access)or OFDM (Orthogonal Frequency Division Multiplex) or other multicarriertransmission mobile communications system has been proposed. Forexample, the methods disclosed in the following four Patent Documents 1to 4 are proposed. Details thereof will be explained later withreference to the drawings, but these may be summarized as follows:

1) A “multiple connection method and apparatus” disclosed in PatentDocument 1 is characterized by dividing a series of subcarriers so as tofreely assign used frequency bands to users.

2) A “mobile station, base station, and mobile communications network”disclosed in Patent Document 2 are characterized in that a subcarrierband dedicated to transmission of control signals is set in thecommunications network.

3) A “channel allocation method” disclosed in Patent Document 3 ischaracterized by changing the number of subcarriers in the series ofsubcarriers in accordance with length of the communications distancebetween the base station and the mobile station.

4) A “wireless transmission apparatus and wireless communicationsmethod” disclosed in Patent Document 4 is characterized by changing thebandwidth of each subcarrier in the series of subcarriers to make thebandwidth of the used frequency band variable.

[Patent Document 1] Japanese Patent Publication (A) No. 9-205411

[Patent Document 2] Japanese Patent Publication (A) No. 2003-264524

[Patent Document 3] Japanese Patent Publication (A) No. 2004-21476

[Patent Document 4] Japanese Patent Publication (A) No. 2002-330467

SUMMARY OF THE INVENTION

The prior arts based on the above four Patent Documents 1 to 4 involvethe following problems:

1) In Patent Document 1 (Japanese Patent Publication (A) No. 9-205411),information on the used subcarrier is not transmitted, therefore thereception side must receive all subcarriers and decode them. This isinefficient.

2) In Patent Document 2 (Japanese Patent Publication (A) No.2003-264524), information on the used subcarrier is transmitted, but itis necessary to receive, demodulate, and decode a common control channelfor transmitting this subcarrier information.

Further, when multiplexing users, the information needed by the usermust be extracted from data transmitted over the common control channel.Further, information directed to each user is contained in that commoncontrol channel, therefore the bandwidth might become insufficient at alow transmission rate. Furthermore, the common control channel is commonto all users, therefore changing the used subcarrier will end up havingan effect on all users. Accordingly, the subcarrier of that commoncontrol channel cannot be easily changed.

3) In Patent Document 3 (Japanese Patent Publication (A) No.2004-214746), the bandwidth of the data channel is made variable, butthe common control channel still uses a fixed frequency band common toall users, so there is the same problem as that of Patent Document 2.

4) In Patent Document 4 (Japanese Patent Publication (A) No.2002-330467), when considering the use of user multiplexing, in order tosuppress interference due to the transmissions for many users, it isnecessary to further perform code multiplexing among users. However, ifthe bandwidths of the subcarriers become different among users, theorthogonality of codes will be deteriorated and will end up becoming acause of interference.

In order to prevent this interference, where a certain user changes thebandwidth of the subcarrier, the other users must also change thebandwidths of the subcarriers to match with that. As a result, thebandwidths of the subcarriers are broadened due to the user in a poortransmission situation, so the transmission efficiency is lowered.Accordingly, there is the inconvenience that changing the bandwidth ofthe subcarrier sometimes will not be an effective means.

Accordingly, in consideration with the above problems, an object of thepresent invention is to provide a communications system (mobilecommunications system) able to freely and easily extend, reduce, orchange the used frequency band of each user within the overall frequencyband allocated to the communications system and preventing the aboveextension, reduction, or change from having an effect on other users,more particularly a communications apparatus (base station and/orterminal) for this purpose.

According to the present invention, as will be explained in detail laterby using the drawings, a specific frequency band is first set from amonga plurality of frequency bands obtaining by dividing the overallfrequency band allocated to the communications system. Then, thatspecific frequency band is used to transmit “used frequency bandinformation” determining which of the remaining frequency bands is to beused between communications apparatuses from one communicationsapparatus to another communications apparatus. Further, that specificfrequency band is set as a “main band” in the above overall frequencyband. This main band transmits the above “used frequency bandinformation” plus “data information (user data)”. Further, among theabove plurality of frequency bands, at least one frequency band set fromamong the frequency bands other than the above “main band” is defined asan “extension band”. This extension band is mainly used for transmittingfurther data information and can deal with an increase of amount ofdata. Accordingly, this extension band is set according to need.However, the above main band is always set at the time of establishmentof a wireless channel. In addition, this main band transmits not onlythe above “used frequency band information”, but also the inherent “datainformation” (user data) within a range permitted by the transmissioncapacity. Further, this main band can include also general “controlinformation” (user control information). Due to this, the above problemsare solved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view showing the basic configuration of a communicationsapparatus (transmission side) according to the present invention.

FIG. 2 is a view showing the basic configuration of a communicationsapparatus (reception side) according to the present invention.

FIG. 3 is a view showing a concrete example of a communicationsapparatus (transmission side) 10 according to the present invention.

FIG. 4 is a view showing a concrete example of a communicationsapparatus (reception side) 20 according to the present invention.

FIG. 5 is a view showing a modification of the communications apparatus(transmission side) 10 according to the present invention.

FIG. 6 is a view showing a modification of the communications apparatus(reception side) 20 according to the present invention.

FIG. 7 is a view showing another modification of the communicationsapparatus (transmission side) 10 according to the present invention.

FIG. 8 is a view showing another modification of the communicationsapparatus (reception side) 20 according to the present invention.

FIG. 9 is a view showing the pattern of frequency division in acommunications system.

FIG. 10 is a view showing a state of selecting one “main band” and“extension band” each.

FIG. 11 is a view showing a first example of a mode of allocation ofmain bands for a plurality of users.

FIG. 12 is a view showing a second example of a mode of allocation ofmain bands for a plurality of users.

FIG. 13 is a flow chart showing an example of dynamically changing thefrequency band of a main band.

FIG. 14A and FIG. 14B are views showing an example of the hardwareconfiguration on the transmission side of pilot signals.

FIG. 15A and FIG. 15B are views showing an example of the hardwareconfiguration on a return side of response (CQI) information to a pilotsignal.

FIG. 16 is a view showing a first example of multiplexing of the pilotsignals.

FIG. 17 is a view showing a second example of multiplexing of the pilotsignals.

FIG. 18 is a view showing an example of the dynamic change of the mainband for easy understanding.

FIG. 19 is a flow chart showing a first example of introduction andallocation of an extension band.

FIG. 20 is a flow chart showing a second example of introduction andallocation of an extension band.

FIG. 21 is a flow chart showing a third example of introduction andallocation of an extension band.

FIG. 22 is a view showing an example of the dynamic change of theextension band for easy understanding.

FIG. 23 is a flow chart showing an example of changing both the mainband and the extension band.

FIG. 24 is a flow chart showing an example of the dynamic change of boththe main band and the extension band for easy understanding.

FIG. 25 is a view showing an example of the hardware configuration onthe return side of response (CQI) information to a pilot signal.

FIG. 26 is a view showing a table for explaining high efficiencytransmission of the used frequency band information.

FIG. 27 is a view showing an example of the dynamic change of theextension band.

FIG. 28 is a view showing a first example of a band extension pattern.

FIG. 29 is a view showing a second example of a band extension pattern.

FIG. 30 is a view showing a third example of a band extension pattern.

FIG. 31 is a view showing an example of the hardware configuration of acommunications apparatus (transmission side) according to Embodiment 10.

FIG. 32 is a flow chart showing an example of the operation in theapparatus of FIG. 31.

FIG. 33 is a view for explaining Embodiment 11.

FIG. 34 is a view showing the gist of the art disclosed in PatentDocument 1.

FIG. 35 is a view showing the gist of the art disclosed in PatentDocument 2.

FIG. 36 is a view showing the gist of the art disclosed in PatentDocument 3.

FIG. 37 is a view showing the gist of the art disclosed in PatentDocument 4.

BEST MODE FOR CARRYING OUT THE INVENTION

First of all, to speed the understanding of the present invention, theprior arts (Patent Documents 1 to 4) explained above will be explainedwith reference to the drawings.

FIG. 34 is a view showing the gist of the prior art disclosed in PatentDocument 1. The figure shows the allocation of frequencies to forexample seven users U1 to U7 (top part). The bottom parts shows detailsof the allocation of a series of subcarrier to the users U1 and U2. Theabscissa is the frequency.

The present system is characterized by consecutively arranging aplurality of carriers for the frequency bands allocated at thetransmission side, dividing them into a plurality of subcarriers inaccordance with the users (U1 to U7), and consecutively arranging these.

Specifically, for example, the overall frequency band able to be used inone communications system is set as 20 MHz, and 250 subcarriers are setthere. Accordingly, the bandwidth of each subcarrier becomes 20MHz/250=80 kHz. Then, these 250 subcarriers are used while beingdynamically allocated among the plurality of users (U1 to U7).

At this time, for example, the subcarriers are dynamically allocated,for example, 50 subcarriers are allocated to a user A (U2) and 75subcarriers are allocated to another user B (U1), to make the number ofsubcarriers used variable.

Along with that, the used frequency band becomes 50×80 kHz=4 MHz for theuser A and becomes 75×80 kHz=6 MHz for the user B. That is, the usedfrequency band is made variable for each user. In this case, it isassumed that the allocated subcarriers are consecutive on the frequencyaxis. Note that it is also possible to further make the sizes of thedivisions of the frequency band variable.

FIG. 35 is a view showing the gist of the prior art disclosed in PatentDocument 2. The figure is a view showing the state of allocation of thecommon control channel and the data channel on the frequency axis.

In the present system, in a multicarrier CDMA system, the subcarriersdedicated to the transmission of the control signal and the subcarriersdedicated to the transmission of data (data channel) are separately set.The common control channel thereof is spread by a unique spread code.Accordingly, when this common control channel is received, it issufficient to demodulate specific subcarriers, so the amount of signalprocessing thereof can be reduced.

FIG. 36 is a view showing the gist of the prior art disclosed in PatentDocument 3. The figure shows making the frequency band of the datachannel in FIG. 35 described above variable in accordance with apropagation distance (communication distance with the base station).Note that the transmission power is changed (large-medium-small).

The present system is a system for realizing variable speedcommunication by making the transmission rate per subcarrier fixed andmaking the number of subcarriers allocated to the user variable. Whenthe distance between the base station and the terminal is short, thetransmission power of each subcarrier is made small and many subcarriersare allocated, while when that distance is long, the transmission powerof each subcarrier is made large and a small number of subcarriers areallocated.

Further, the number of subcarriers used for the common control channelis made small, while a large number of subcarriers are allocated withrespect to the data communications use channel (data channel). The twoare completely separately arranged along the frequency axis. Note thatthe subcarriers dedicated to the common control channel are used tonotify the center subcarrier number of the subcarriers allocated for thedata channel and the number of used subcarriers from the base station tothe mobile station.

FIG. 37 is a view showing the gist of the prior art disclosed in PatentDocument 4. The figure shows that the bandwidth of each subcarrier ismade variable in accordance with whether or not the propagationenvironment is good.

The present system changes the bandwidth of each subcarrier while makinga total number of subcarriers constant in accordance with the conditionof the propagation environment in wireless transmission. For example,when the propagation condition becomes poor, the band of each subcarrieris made wider. Due to this, the transmission can be carried out withoutchanging the total subcarriers, therefore the transmission rate can bemaintained constant without regard to the propagation environment.

The present invention solves the already explained problems of the priorarts (Patent Documents 1 to 4) explained with reference to FIG. 34 toFIG. 37 explained above. This will be explained in detail below withreference to the drawings.

FIG. 1 is a view showing the basic configuration of a communicationsapparatus (transmission side) according to the present invention, andFIG. 2 is a view showing the basic configuration of a communicationsapparatus (reception side) according to the present invention.

In FIG. 1, reference numeral 10 indicates the communications apparatus(transmission side), and in FIG. 2, reference numeral 20 indicates thecommunications apparatus (reception side). These are accommodated in thesame communications system (mobile communications system). Note that asalready explained, the communications apparatus 10 may be a base stationand the communications apparatus 20 may be a terminal, or vice versa.The present invention can be applied to both cases, but for easierunderstanding, in the following explanation, the communicationsapparatus 10 on the transmission side will be assumed as the basestation, and the communications apparatus 20 on the reception side willbe assumed as a terminal unless otherwise indicated.

First, referring to FIG. 1, the selection function in particular of aused frequency band selecting/setting unit 15 is used to select the usedfrequency band to be used with the other communications apparatus 20.The “used frequency band information” If (frequency) according to thisselection is input to a transmission data generation unit 11 wheretransmission data Dt (transmission) combined integrally withtransmission data (user data) Du (user) to be transmitted to thecommunications apparatus 20 is generated. Accordingly, the transmissiondata Dt includes the transmission data Du and the used frequency bandinformation If, but in actuality further includes also other“communication control information” Ict (control). This information Ictis the information concerning a used modulation scheme for example QAMand information etc. concerning a one time transmission data amount ofthe transmission data Du.

The above transmission data Dt is modulated in a predetermined way at amodulation unit 12, then input to the next multicarrier transmissionsender unit 13. This sender unit 13 is supplied with a band setinstruction signal Sb (band) instructing processing for transmission atthe above selected used frequency band by the setting function of theabove used frequency band selecting/setting unit 15. The sender unit 13performs the processing for signal transmission by multicarriertransmission at the frequency band based on this signal Sb.

Further, a wireless unit 14 converts the frequency conversion of thetransmission data signal St from the above sender unit 13 and transmitsthis from the next antenna AT toward another communications apparatus(terminal) 20.

On the other hand, referring to FIG. 2, the wireless signal from theabove antenna AT (FIG. 1) is received at the antenna AT (FIG. 2) andfurther converted in frequency by a wireless unit 21 to be a receiveddata signal Sr which is then input to a multicarrier transmissionreceiver unit 22. This receiver unit 22 processes the received datasignal Sr for signal reception according to the multicarriertransmission, then the next demodulation unit 23 demodulates the signalafter the signal reception processing.

The demodulated received data Dr is decoded at a received data decodingunit 24 and separated to the original transmission data Du and thepreviously set used frequency band information If explained before.Further, the above communication control information Ict is alsoseparated from that data Dr. Note that the units to be controlledaccording to this information Ict are not directly related to the gistof the present invention, so explanations are omitted.

As explained above, the original used frequency band information Ifobtained by separation from the received data Dr is input to a usedfrequency band setting unit 25. The setting unit 25 receives thisinformation If and reproduces the above band set instruction signal Sb.This signal Sb is supplied to the above multicarrier transmissionreceiver unit 22, then this receiver unit 22 performs processing forsignal reception according to the multicarrier transmission by using thefrequency band selected on the transmission side. Note that thepreviously determined frequency band may be selected in the initialstage of establishment of the wireless channel.

In the present invention, the transmission side (10) and the receptionside (20) can use the same used frequency band by the above-explainedband set instruction signal Sb. Further, based on that signal Sb, thatused frequency band can be simultaneously extended, reduced, or changedat both of the transmission side (10) and the reception side (20). Thus,the object of the present invention explained before can be achieved.

The basic configuration of the present invention explained above will beexplained a little more concretely in comparison with the above priorarts.

In the present invention, the frequency band usable in thecommunications system as a whole is divided into a plurality of bands.For example, when the used frequency band of the communications systemas a whole is set as 20 MHz, it is divided into four bands of 5 MHzeach. One band 5 MHz is used to transmit the information of the controlchannel for transmitting the used frequency band information and thetransmission channel (data channel) for transmitting the transmissiondata.

According to the present invention, as explained before, the frequencyband for transmitting at least the control channel is defined as the“main band” and a further extended frequency band is defined as an“extension band”. For example, when considering this in an OFDMcommunications system, 100 subcarriers are included in one band 5 MHz,the bandwidth of each subcarrier is 50 kHz, and the information of thecontrol channel and the data channel are transmitted by using the seriesof these 100 subcarriers. The two information may be multiplexed by timedivision multiplexing, frequency division multiplexing, or code divisionmultiplexing.

As explained above, unlike Patent Document 3 (Japanese PatentPublication (A) No. 2004-214746), the information of the “main band” isreceived and decoded to learn the used frequency band (or number of usedfrequency bands), therefore, the used frequency band can be easilyextended, reduced, and changed. Further, due to this, unlike PatentDocument 1 (Japanese Patent Publication (A) No. 9-205411) and PatentDocument 3 (Japanese Patent Publication No. 2004-214746), theconfiguration of the reception unit is simplified.

Further, if making the number of subcarriers per frequency bandconstant, the number of subcarriers will change with a ratio of a wholenumber along with a change of the number of used frequency bands.Accordingly, when compared with Patent Document 3 (Japanese PatentPublication (A) No. 2004-214746) in which the subcarriers dynamicallychange, the configuration of the reception unit is simplified.

Further, by designating the used frequency band from the base station tothe terminals in advance, the extension band described above can beeasily changed and added to and even the main band can be changed.

Further, if making the bandwidth of each subcarrier fixed as explainedabove, the used frequency band can be changed without influencing otherusers as in Patent Document 4 (Japanese Patent Publication (A) No.2002-330467). Various embodiments according to the present inventionwill be explained below.

Embodiment 1 Setting of Used Frequency Band

First, describing some characteristic features disclosed in the presentEmbodiment 1, these are as follows. The principal points of thesecharacteristic features are as already described and reside in thefollowing three points (i) to (iii):

(i) A specific frequency band from among a plurality of frequency bandsformed by dividing the overall frequency band allocated to acommunications system is set, and that specific frequency band is usedto transmit “used frequency band information” If determining whichremaining frequency band is to be used between communicationsapparatuses (10, 20), (ii) that specific frequency band is set as a“main band” in the overall frequency band, and that main band transmits,in addition to the used frequency band information If, data informationDu, and (iii) among the above-explained plurality of frequency bands, atleast one frequency band set from among the frequency bands other thanabove “main band” is defined as an “extension band”, and that extensionband mainly transmits further data information (Du).

Next, some principal points further disclosed in the present Embodiment1 reside in the following four points (iv) to (vii):

(iv) The above “main band” is set fixedly at the time of theestablishment of the wireless channel between the communicationsapparatuses (10, 20),

(v) when there are a plurality of communications apparatuses (20), “mainbands” are individually set for the above plurality of frequency bandsand, at the same time, main bands are individually assignedcorresponding to these plurality of communications apparatuses (20),

(vi) two or more communications apparatuses (20) can simultaneously usethe same “main band” by time division multiplexing and/or code divisionmultiplexing, and

(vii) further, the number of extension bands is changed in accordancewith the predetermined transmission rate of the data information (Du).

FIG. 3 is a view showing a concrete example of the communicationsapparatus (transmission side) 10 according to the present invention, and

FIG. 4 is a view showing a concrete example of the communicationsapparatus (reception side) 20 according to the present invention. Notethat, same components will be indicated by same reference numerals orsymbols throughout all of the figures. Further, the concrete examplesshown in FIG. 3 and FIG. 4 are not only applied to the presentEmbodiment 1, but also commonly applied to the other Embodiments 2 to 10explained later.

Referring to the communications apparatus (transmission side) 10 first,the parts corresponding to the components 11 to 15 and Du, Dt, St, andSb shown in FIG. 1 are shown assigned these reference numerals orsymbols 11 to 15 and Du, Dt, St, and Sb.

The transmission data generation unit 11 is configured by a data blockpreparation unit 31, an encoding unit 32, a transmission data amountcalculation unit 33, an encoding unit 34, and a multiplexing unit (Mux)35 according to the example of the present figure.

Based on the used frequency band information If from the above usedfrequency band selecting/setting unit 15, the transmission data amountcalculation unit 33 first calculates a transmission data length, thenthe data block preparation unit 31 prepares data blocks for eachtransmission data length. Further, the encoding unit 32 encodes thetransmission data by using that transmission data length.

The above used frequency band information If is encoded together withthe communications control information Ict indicating the usedmodulation scheme etc. at the encoding unit 34. Note that the encodingunits 32 and 34 may encode Du and If all together as one encoding unit.

The encoded outputs from the two encoding units 32 and 34 aremultiplexed at the multiplexing unit (Mux) 35 and become the alreadyexplained transmission data Dt. This data Dt is further modulated at themodulation unit 12 as explained before. As the method of thismultiplexing, there are frequency division multiplexing separatingsubcarriers and using the same, time division multiplexing (by using forexample a frame format shown in FIG. 16), code division multiplexingetc. Further, as the modulation scheme by the modulation unit 12, thereare QPSK, 16QAM, 64QAM, etc.

Next, when looking at the multicarrier transmission sender unit 13, inthe example shown in the present figure, this is configured bycomponents 36, 37, 38, 39, and 40. Note that this is shown as an examplebased on communications according to OFDM. Another example based oncommunications according to MC-CDMA is shown in FIG. 7 (FIG. 8).

The demultiplexing unit (DeMux) 36 demultiplexes this into theinformation belonging to the “main band” and the information belongingto the “extension bands”. The information belonging to the “main band”is converted to a parallel signal at a serial/parallel converter (S/P)37, then a time-frequency transform is applied to the parallel signal atan Inverse Fast Fourier Transform unit (IFFT) 38. The parallel signaltransformed into frequency is converted to a serial signal again at aparallel/serial converter (P/S) 39. Further, a guard interval (GI)insertion unit 40 inserts a guard interval GI into the serial signal forpreventing inter-symbol interference.

The thus obtained transmission data signal St is input to the wirelessunit 14. This wireless unit 14 is, according to the example of thepresent figure, configured by a general mixer 41, a local oscillator 42,and a power amplifier 44 (a D/A converter, a filter, etc. are omitted)and transmits the transmission data signal St from the antenna At. Inthis case, an adder unit 43 is provided in the middle.

The adder unit 43 applies the same processing as the processing for the“main band” by the above-explained components 37, 38, 39, 40, 41, and 42with respect to the information belonging to the above “extension bands”demultiplexed at the demultiplexing unit (DeMux) 36 as explained beforeby the components 37′, 38′, 39′, 40′, 41′, and 42′, obtains thetransmission data signal St on the “extension band” side, and combinesthe same together with the already explained transmission data signal Ston the “main band” side.

The transmission data on the “extension band” side described above isgenerated only when data transmission by the “extension bands” isneeded. Whether or not it is needed is determined according to the bandset instruction signal Sb from the already explained selecting/settingunit 15.

Referring to FIG. 4 next, parts corresponding to the components 21 to 25and Sr, Dr, Du, If, and Sb shown in FIG. 2 are shown assigned thereference numerals 21 to 25 and symbols Sr, Dr, Du, If, and Sb.

The wireless unit 21, according to the example of the present figure,eliminates an undesired band of a signal in the signal received from theantenna AT by a band pass filter (BPF) 51, converts the remainder to apredetermined reception frequency by the mixer 52 and the localoscillator 53, and thereby obtains the received data signal Sr.

This received data signal Sr is input to the multicarrier transmissionreceiver unit 22 and processed. This receiver unit 22 is, according tothe example of the present figure, configured by the components 54, 55,56, 57, and 58.

First, the guard interval (GI) elimination unit 54 eliminates the guardinterval inserted at the transmission side. The signal after the GIelimination is further converted to a parallel signal at theserial/parallel converter (S/P) 55. The Fast Fourier Transform unit(FFT) 56 applies a frequency-time transform to the parallel signal. Thetime transformed parallel signal is converted to a serial signal againat the parallel/serial converter (P/S) 57.

On the other hand, when the signal received from the antenna AT containsinformation belonging to an “extension band”, the mixer 52′ and thelocal oscillator 53′ extract the signal of the “extension band” andapply the same processing as the processing by the above-explainedcomponents 55 to 57 by the same components S/P 55′, FFT 56′, and P/S 57′to obtain a time-transformed serial signal.

The serial signals from the above parallel/serial converters 57 and 57′are multiplexed at the multiplexing unit (Mux) 58 and furtherdemodulated at the demodulation unit 23. Note that when only informationbelonging to the “main band” is transmitted, the above multiplexing unit58 does not perform the multiplexing, but only passes the signaltherethrough.

The signal from the multiplexing unit 58 becomes the received data Drdemodulated at the next demodulation unit 23, then is input to thereceived data decoding unit 24. This decoding unit 24 is, according tothe example of the present figure, configured by a demultiplexing unit(DeMux) 59, a data channel decoding unit 60, a control channel decodingunit 61, and a transmission data amount calculation unit 62.

The above demultiplexing unit 24 demultiplexes the received data Dr todata channel side data and control channel side data and distributesthese to the decoding unit 60 and the decoding unit 61. From thedecoding unit 60, the original transmission data Du is reproduced basedon the transmission data amount explained later. On the other hand, fromthe decoding unit 61, the “used frequency band information” If isreproduced.

The above information If from the decoding unit 61 is input to thetransmission data amount calculation unit 62 on the one hand, the datalength of the received transmission data is calculated here based onthat If, and the transmission data is decoded by the above decoding unit60 based on this data length.

The above information If from the decoding unit 61 is given to thealready explained used frequency band setting unit 25 on the other hand,where the above band set instruction signal Sb is generated. Then,according to the content of this signal Sb, the circuit portions (22,58, 59) are set corresponding to the selected frequency band by theshown dotted line route. Note that the received data decoding unit 24 ofFIG. 4 may be configured so that the received data Dr is input to onedecoding unit (making the decoding units 60 and 61 common) at first anddecoded, then demultiplexed to the data channel and the control channelat the demultiplexing unit 59.

In the configuration of FIG. 3 and FIG. 4 explained above, the frequencyband of the “main band” is fixed, and only the frequency bands of the“extension bands” are variable. However, in a certain embodiment of thepresent invention, not only the “extension bands”, but also the “mainband” can be made variable in frequency bands. An example of aconfiguration accomplishing this is shown in the drawings.

FIG. 5 is a view showing a modification of the communications apparatus(transmission side) 10 according to the present invention, and FIG. 6 isa view showing a modification of a communications control device(reception side) 20 according to the present invention.

The difference between the configuration shown in these FIG. 5 and FIG.6 and the configuration shown in FIG. 3 and FIG. 4 explained beforeresides in that, in FIG. 5, the scope of instruction by the band setinstruction signal Sb from the used frequency band selecting/settingunit 15 reaches not only the “extension band” side (37′ to 42′) (case ofFIG. 3), but also the “main band” side (37 to 42). Further, thedifference resides in that, in FIG. 6, the scope of instruction by theband set instruction signal Sb from the used frequency band setting unit25 reaches not only the “extension band” side (52′ to 57′) (case of FIG.4), but also the “main band” side (52 to 57). Thus, the change of thefrequency band of the “main band” also becomes possible.

Further, the explanation of the concrete example explained above waspredicated on communications by OFDM, but other than this, it is alsopossible to explain it based on communications according to the MC-CDMA.Also, an example of the communications apparatus in this latter case(MC-CDMA base) is shown here.

FIG. 7 is a view showing another modification of the communicationsapparatus (transmission side) 10 according to the present invention, andFIG. 8 is a view showing another modification of the communicationsapparatus (reception side) 20 according to the present invention.

For example, when comparing the above FIG. 5 and FIG. 6 and the presentFIG. 7 and FIG. 8, on the transmission side (10), the configuration ofthe multicarrier transmission sender unit 13 is different, and on thereception side (20), the configuration of the multicarrier transmissionreceiver unit 22 is different.

Namely, in the sender unit 13 shown in FIG. 7, the difference resides inthe point that a copier unit 46 and a multiplication unit 47 are used.Further, in the receiver unit 22 shown in FIG. 8, the difference residesin the point that a multiplication unit 65 and a combining unit (E) 66are used.

First, the transmission operation will be explained by using FIG. 7. Thegenerated transmission data is modulated and copied by the number ofsubcarriers at the copier unit 46. The multiplication unit 47 multipliesthe copied signals by spread codes (C1, C2 . . . Cn). The IFFT units(38, 38′) apply IFFT to the results to apply a time-frequency transform.Then, the GI insertion unit 40 inserts a GI, then the signal isconverted in frequency and transmitted from the antenna AT. Further, thesetting of the multicarrier transmission sender 13 is changed based onthe used frequency band selected at the used frequency band selectionunit 15.

Next, a reception operation will be explained by using FIG. 8. First,the received signal is frequency converted to obtain a base band signal,then the GI is eliminated at the GI elimination unit 54. Next, thesignal is converted from a serial to parallel format (55, 55′), and eachof the parallel signals is multiplied by the spread codes (C1, C2 . . .Cn) at the multiplication unit 65 and despread. The results thereof aresubjected to FFT at the FFT units (56, 56′), a frequency-time transformis carried out, then the results are summed up at the combining unit 66.The result of this is demodulated at the demodulation unit 23. Below,the same processing as that explained before is carried out to extractthe used frequency band information If. Then, based on the extractedused frequency band information If, the setting of the multicarriertransmission receiver unit 22 is changed. Note that, in FIG. 7 and FIG.8, when the used frequency band is changed, the number n of codes thefrequency spread may be made variable. When MC-CDMA is used as describedabove, the hardware configuration can be simplified in comparison withthe OFDM. Further, on the other hand, there arises a necessity of makingthe number of point of FFT and IFFT dynamically variable, so the controlbecomes complex.

Below, the present Embodiment 1 will be further explained with referenceto the arrangement of the frequency bands.

A communications system able to change the used frequency band usingOFDM etc. transmits the used frequency band information If by using aspecific frequency band. Then, by demodulating and decoding the specificfrequency band, the used frequency band If can be obtained. By thisinformation If, the communications in an extension band become possible.This is based on division of the overall frequency band as follows inthe present invention.

FIG. 9 is a view showing the pattern of frequency division in acommunications system. The series of subcarriers of the present figureshow the overall frequency band assigned to the communications system.This overall frequency band is divided into a plurality of frequencybands. In the present figure, the example of division into four isshown, that is, the band is divided into four frequency bands, that is,“BAND 1”, “BAND 2”, “BAND 3”, and “BAND 4”. Then, any of these “BAND 1”to “BAND 4” is selected and defined as the above “main band”, whileanother band is selected and defined as an above “extension band”.

FIG. 10 is a view showing the state of selecting one “main band” and one“extension band”. For example the above band 1 is selected as the “mainband”, and for example the above band 2 is selected as an “extensionband”. As explained before, the “main band” is assigned to thetransmission of the control channel (CH) and the data channel (CH), andthe “extension band” is assigned to the further transmission of the datachannel. The main band used by a certain terminal is determined by forexample the base station or the higher base station controller.Alternatively, converse to this, the main band may be designated fromthe terminal side to the base station side.

The above main band may be fixed in advance in the communications systemor may be set at the time of establishment of a wireless channel betweencommunications apparatuses (base station and terminal). The setting maybe fixed until the communication is completed.

Further, when there are a plurality of communications apparatuses (userterminals), a different main band may be set for each user terminal.This situation will be shown in the figure.

FIG. 11 is a view showing a first example of a mode of assignment ofmain bands for a plurality of users, and FIG. 12 is a view showing asecond example of a mode of assignment of main bands for a plurality ofusers. Note that these modes can also be applied to extension bands.

Referring to FIG. 11 first, main bands of users U1 to U4 areindividually assigned to a plurality of frequency bands, that is, band 1to band 4. Note that, in this case, the number of users is restricted bythe number of bands.

Therefore, as shown in FIG. 12, the same main band is simultaneouslyassigned with respect to a plurality of communications apparatuses (userterminals). This becomes possible by user multiplexing. As thismultiplexing method, there are time division multiplexing and codedivision multiplexing or multiplexing combining these.

Further, in the present Embodiment 1, also the number of used frequencybands (band 1 to band 4) can be changed in accordance with thepredetermined transmission rate of the data information (transmissiondata Du).

Namely, the base station considers the communication situation,propagation environment, used frequency band, etc. of other terminals inthe middle of communications. When judging that another frequency bandcan be used, it extends the used frequency band. Note that at the timeof extension, the available frequency can be extended on a prioritybasis according to the degree of priority of communications between theterminals, the predetermined transmission rate, and other transmissiondata attributes (QoS: Quality of Service).

In this way, since the used frequency band information If is transmittedby using a specific frequency band (main band), the reception side needonly receive that main band first and does not have to receive anddemodulate and decode up to the other frequency bands. Further, by usingthe extension band, a further speed-up of the transmission rate becomespossible, and an improvement of the frequency utilization efficiency canbe achieved.

Embodiment 2 Dynamic Change of Main Band

First, describing some characteristic features disclosed in the presentEmbodiment 2, they are as follows:

i) The frequency band occupied as the main band among the plurality offrequency bands (band 1 to band 4) is made variable along with theelapse of time,

ii) whether or not the propagation environment between communicationsapparatuses (10, 20) is good is judged, then the frequency band of thebest propagation environment among the above plurality of frequencybands or the frequency band next to this is selected and set as the mainband,

iii) at the time of new setting of the main band, the change of thefrequency band is notified to the communications apparatus of the otherparty in advance,

iv) the result of detection of the transmission quality (CQI) obtainedin response to a pilot channel or pilot signal transmitted betweencommunications apparatuses is used to judge whether or not theabove-explained propagation environment is good,

v) the judgment of whether or not the propagation environment is good isperformed for all of the above plurality of frequency bands sequentiallyor simultaneously; and

vi) further, the result of judgment of the quality of the propagationenvironment is sent to the communications apparatus of the other partyby using the control channel of a specific frequency band.

In general, the transmission characteristic of the control channel mustbe better in terms of the transmission quality in comparison with thedata channel. First, this is because the channel through which the datais to be transmitted must be reliably set. Namely, the main bandincluding the control channel must select the frequency band having abetter propagation environment so that the transmission quality thereofbecomes good in comparison with the extension band. Therefore, aconcrete example of free selection of the frequency band set as the mainband in accordance with quality of the propagation environment will beexplained.

FIG. 13 is a flow chart showing an example of dynamically changing thefrequency band of a main band. Note that the basictransmission/reception operation between the base station and a terminalis as explained in the above Embodiment 1. Further, in FIG. 13, eachsolid line block represents an operation of the base station, and eachdotted line block represents an operation of the terminal. Note that thereverse may also apply (true for other flow charts explained later aswell).

Step S11: Send pilot channel signal at each frequency band.

Step S12: Receive all pilot channel signals,

Step S13: Calculate each SNR etc. and convert it to CQI, and

Step S14: Transmit each CQI by uplink control channel.

Step S15: Receive each CQU,

Step S16: Select used frequency band and determine timing of change ofband, and

Step S17: Transmit the selected used frequency band and determinedchange timing by downlink control channel.

Step S18: Receive the above used frequency band and change timing,

Step S19: Change setting for each circuit unit at the above changetiming, and

Step S20: Start reception operation by using main band after thatchange.

Note that the above SNR indicates the signal to noise ratio, and CQI achannel quality indicator. Note that a definition indicating CQI isdescribed in TS25.212 Release 5 etc. of 3GPP (3rd Generation PartnershipProject http://www.3gpp.org/). The specifications are recorded athttp://www.3gpp.org/ftp/Specs/html-info/25-series.htm.

The processing for making the main band variable along with the elapseof time according to the above flow chart showing one example in FIG. 13can be accomplished by for example the following hardware configuration.

FIGS. 14A and 14B are views showing an example of the hardwareconfiguration of the transmission side of the pilot signal, and FIGS.15A and 15B are views showing an example of the hardware configurationof the return side of the response (CQI) information to the pilotsignal.

The configurations shown in FIGS. 14A and 14B are substantially the sameas the configuration of FIG. 3 (or FIG. 5) explained before. Theelements to be newly noted are a pilot signal Sp (or pilot channel) onthe left end of FIG. 14A, and a multiplexing unit (Mux) 71 formultiplexing the pilot signal Sp and the used frequency band informationIf and a CQI extraction unit 72 in FIG. 14B. The configuration of thisFIG. 14B is substantially the same as the configuration of FIG. 4 (orFIG. 6) explained before. The component to be newly noted is a CQIextraction unit 72 on the lower side of the center of the presentfigure. Note that, in FIG. 14B, units corresponding to those in FIG. 4are given the reference numerals 52, 53, 54, . . . used in FIG. 4 plus100 and thereby indicated as 152, 153, 154, . . . .

Further, the configurations shown in FIGS. 15A and 15B are the same asthe configuration of FIG. 4 (or FIG. 6) explained before. The componentsto be newly noted are an SNR measurement unit 75 and a CQI calculationunit 76 in FIG. 15A and further an encoding unit 78 and an adder unit 79in FIG. 15B after passing through a loop back path 77. Note that in FIG.15A, parts corresponding to those in FIG. 4 (reception side) areindicated by using the reference numerals 52, 53, 54, . . . used in FIG.4, while in FIG. 15B, parts corresponding to those in FIG. 3(transmission side) are given the reference numerals 12, 37, 38, . . .used in FIG. 3 plus 100 and thereby indicated as 112, 137, 138, . . . .

The above pilot signal Sp is transmitted after multiplexing with othertransmission information in actual operations. This multiplexing methodincludes for example the following two schemes:

FIG. 16 is a view showing an example of first multiplexing of a pilotsignal, and FIG. 17 is a view showing an example of second multiplexingof a pilot signal. Note that, in both figures, “P” represents the pilotsignal Sp, “C” represents the already explained communication controlinformation Ict, and “D” represents the already explained transmissiondata Du.

FIG. 16 shows that the pilot signal Sp is multiplexed along with theelapsed time, while FIG. 17 shows that the pilot signal Sp ismultiplexed along with both the elapsed time and the frequency.

FIG. 18 is a view showing an example of the dynamic change of the mainband in the above-explained Embodiment 2 for easier understanding. Timeelapses from the top toward the bottom in the present figure. Along withthe elapse of time, the main band changes as for example “BAND 1”→“BAND2”→“BAND 3”→“BAND 4” following the better propagation environment.

Thus, the base station multiplexes the signal for measuring thepropagation environment (pilot) in all of the frequency bands used andtransmits this as the control channel. Note that, in actual use, a casenot including the transmission data Du is also assumed. Further, thepilot channel may be provided in place of the pilot signal Sp.

The terminal receives the pilot channel signals for all frequency bands(band 1 to band 4), measures the reception conditions and propagationenvironments, for example the SNR and CIR (carrier to interferenceratio), calculates the above CQIs from the measurement values, andsequentially or simultaneously transmits the same to the base stationfor each band by using the uplink control channel. Note that it may alsotransmit the measurement results of the above CIR and SNR as they are.

The base station receives the uplink control channel signal anddemodulates and decodes the CQIs. It selects the frequency band havingthe best CQI value from among the plurality of CQIs as the main band. Itsends this selection result and the timing of change of the main band onthe downlink control channel to the terminal.

The terminal receives this downlink control channel signal anddemodulates and decodes this to extract the information of the usedfrequency band and timing of change. Then, at the timing of change, itchanges the used frequency band. Note that the timing of change may bedetermined according to for example an absolute time or relative time ora slot unit. Further, it is also possible not to transmit the timing ofchange, but set it as after, e.g., 5 slots from the transmission of thedownlink control channel signal etc. and thereby fix it for the system.

In the above description, the frequency band having the best propagationenvironment was selected as the main band, but a case where the bestfrequency band cannot be selected due to the situation of the otherterminal may also be considered. In such case, the second best frequencyband next to that may be selected.

Note that here the main band was selected by the base station, but theterminal may similarly select the frequency band having the bestpropagation environment and transmit this to the base station.

The SNRs, CIRs, etc. may be measured in the terminal simultaneously forall frequency bands as explained above or in a time division manner.Further, in a situation where bands having narrow frequency band widthscontinue, the propagation environment will not largely vary, therefore,in such case, only one frequency band need be measured. Further, themeasurement value thereof may be made a mean value after measurementover a certain time.

Further, in Embodiment 1, the extension band was explained by assumingtransmission of only the transmission data Du, but to measure thepropagation environment of each frequency band, in addition to thetransmission data Du, a pilot channel or pilot signal may also betransmitted.

The above explanation was given with reference to transmission from thebase station to a terminal, but the present invention can similarly beconversely applied to transmission from a terminal to the base station.

As already explained, in general, the transmission characteristic of thecontrol channel must be better than the transmission characteristic ofthe data channel in transmission quality. Accordingly, for the main bandincluding the control channel, it is necessary to select a frequencyband having a good propagation environment. According to theabove-explained operation, it becomes possible to select a frequencyband under the best propagation environment as the main band. Further,even when the propagation environment changes along with the elapse oftime, it becomes possible to always select the frequency band under thebest propagation environment as the main band.

Due to this, not only the transmission error of the control channelinformation is reduced, but also the hardware settings of the receptionside become easy, and improvement of the transmission quality becomespossible. Further, it is also possible to reduce the number of times ofdata retransmission due to transmission error, therefore thetransmission rate can be further increased.

Further, the main band is variably set, therefore unbalance of theutilization situation (load) among frequency bands can be avoided andimprovement of the frequency utilization efficiency can be achieved.

Embodiment 3 Dynamic Change of Extension Band

Describing some characteristic features disclosed in the presentEmbodiment 3 first, they are as follows:

i) The frequency band set as an extension band among a plurality offrequency bands (band 1 to band 4) is made variable along with theelapse of time,

ii) whether or not the propagation environment between communicationsapparatuses (10, 20) is good is judged, and the frequency band next tothe frequency band having the best propagation environment among theabove plurality of frequency bands is selected and set as the extensionband.

iii) Further, the frequency band usable by the communicationsapparatuses (10, 20) is restricted at the time of establishment of thewireless channel, and the main band and the extension band aredynamically assigned within that restricted frequency band.

iv) Furthermore, the setting information of the frequency band to be setas the extension band is notified to the communications apparatus of theother party in advance for the extension,

v) frequency band setting information concerning the frequency band forwhich extension is possible or change is possible is received from thecommunications apparatus of the other party, and the extension band ormain band is changed by this, and

vi) further, change timing information concerning the timing of thechange is received.

vii) Further, the result of judgment as to whether or not thepropagation environment is good is transmitted to the communicationsapparatus of the other party by using a control channel of a specificfrequency band,

viii) whether or not the propagation environment is good is judged usingthe result of detection of the transmission quality (CQI) returned inresponse to pilot channels or pilot signals transmitted between thecommunications apparatuses (10, 20),

ix) based on at least one of the available frequency band of the relatedcommunications apparatus, the quality of the propagation environment ateach frequency band, the usage situation of each frequency band, and thepredetermined transmission rate of the data information (Du), thenecessity of the setting or change of the extension band is judged, and

x) at the time of new setting of the above extension band, the change ofthe frequency band is notified to the communications apparatus of theother party in advance.

FIG. 19 is a flow chart showing a first example of the introduction andchange of an extension band,

FIG. 20 is a flow chart showing a second example of the introduction andchange of an extension band, and

FIG. 21 is a flow chart showing a third example of the introduction andchange of an extension band.

Specifically, FIG. 19 shows a control flow in a case of selecting anextension band by using the used frequency band of the terminal and theCQI of each frequency band. Further, FIG. 20 shows a control flow in acase of selecting an extension band by using the used frequency bandthereof, the usage situation of each frequency band, and thepredetermined transmission rate of the transmission data. Further, FIG.21 shows a control flow in a case of selecting an extension band byusing the used frequency band of the terminal, the CQI of each frequencyband, the usage situation of each frequency band, and the predeterminedtransmission rate of the transmission data.

In FIG. 19,

Step S21: Transmit available frequency band.

Step S22: Receive available frequency band, and

Step S23: transmit pilot channel signals by using available frequencyband.

Step S24: Receive all pilot channel signals, calculate SNRs etc., andconvert it to CQIs, and

Step S25: transmit CQIs through uplink control channel.

Step S26: Receive above CQIs,

Step S27: select existence of need of extension from CQIs, selectextended frequency band, and determine timing of change thereof, and

Step S28: transmit extended frequency band and timing of change throughdownlink control channel.

Step S29: Receive above extended frequency band and timing of change,

Step S30: change setting for each circuit part at the timing of change,and

Step S31: start reception operation by using extension band after thatchange.

Next, in FIG. 20,

Step S41: transmit available frequency band.

Step S42: Receive above available frequency band,

Step S43: confirm usage situations of frequency bands and predeterminedtransmission rate of transmission data Du,

Step S44: select existence of necessity for extension, select extendedfrequency band, and determine timing of change thereof, and

Step S45: transmit extended frequency band and timing of change throughdownlink control channel.

Step S46: Receive above extended frequency band and timing of change,

Step S47: change setting for each circuit unit at the timing of change,and

Step S48: start reception operation by using extension band after thatchange.

Further, in FIG. 21,

Step S51: transmit available frequency band.

Step S52: Receive available frequency band, and

Step S53: transmit pilot channel signals by using available frequencyband.

Step S54: Receive all pilot channel signals, then calculate SNRs etc.,convert to CQIs, and

Step S55: transmit above CQIs through uplink control channel.

Step S56: Receive above CQIs,

Step S57: confirm usage situations of frequency bands and predeterminedtransmission rate of transmission data Du,

Step S58: select existence of necessity for extension, select extendedfrequency band, and determine timing of change thereof, and

Step S45: transmit extended frequency band and timing of change throughdownlink control channel.

Step S60: Receive above extended frequency band and timing of change,

Step S61: change setting for each circuit unit at the timing of change,and

Step S62: start reception operation by using extension band after thatchange.

In the present Embodiment 3, dynamic change of the extension band isexplained. In general, at the time of the setting of a channel (time ofestablishment of wireless channel), the frequency band available by aterminal is transmitted from the terminal to the base station (or basestation controller). This is the above-explained terminal availablefrequency band. Note that an explanation will be given by assuming acase where this available frequency band is notified, but it may also beconsidered not to perform such notification in a case where theavailable frequency band is previously determined in the communicationssystem.

In the same way as the case of the above Embodiment 2, the base stationtransmits pilot signals Sp, and a terminal transmits the above CQIscalculated based on the received pilot signals Sp to the base station.Next, the base station considers the available frequency band of theterminal, the CQI of each frequency band transmitted from the terminal,the utilization situation of the other terminals, the predeterminedtransmission rate of the data Du to be transmitted, and so on and judgesif the frequency band must be extended (used frequency band must bechanged) for that terminal.

When extending is needed, the frequency band is selected. Further, theabove timing of change when extending the used frequency band isselected. Then, the selection information of this extension band and theabove timing of change are transmitted by using the control channel. Theterminal receiving this control channel signal changes the setting ofeach circuit unit in the terminal based on the information for theextension band and the timing of change, then starts the reception byusing that extension band.

This operation will be supplementarily explained next. However, refer tothe control flow of FIG. 21 explained before. First, the terminaltransmits the frequency band useable by that terminal to the basestation or its higher base station controller etc. The base stationreceiving this transmits pilot channel signals or pilot signals Sp byusing that used frequency band. Note that when transmitting pilotchannel signals using a common channel common to all terminals, theselection of the used frequency band is not needed.

The terminal receiving the pilot channel signals via the frequency bandscalculates the above CQIs based on the above CIRs, SNR, etc., andtransmits the CQI calculated values to the base station through theuplink control channel. The base station receiving these considers theCQIs, the utilization situations of the frequency bands, thepredetermined transmission rate of the transmission data Du, and otherQoS, selects the existence of the necessary for extension and the usedfrequency band in the case where the extension is carried out,determines the timing of change of the band, and notifies theinformation to the terminal via the downlink control channel.

The terminal receiving the information sets or re-sets each circuit unitof the terminal at the above timing of change and receives signals byusing the extension band after the change at the above timing of change.

FIG. 22 is a view showing an example of the dynamic change of theextension band in the present Embodiment 3 for easier understanding. Theelapse of time goes from the top toward the bottom in the presentfigure. As this elapse of time, the extension band is set as “BAND2”→“band 2+band 3+band 4” exemplified in the figure whenever there is anecessity of extension while selecting a good frequency band next bestto the frequency band having the best propagation environment. As in thelatter case, the expansion band may be set by combining a plurality ofbands.

In this way, the frequency band having a relatively good propagationenvironment can be selected as the extension band for a propagationenvironment changing along with the elapse of time. Due to this, thetransmission error of the control channel information is reduced, thehardware setting of the reception side becomes easier, and theimprovement of the transmission quality becomes possible. Further, thenumber of times of resending the data can be decreased, therefore thetransmission rate can be enhanced. Further, if considering theprocessing time for correcting the settings on the reception side andnotifying the change of the extension band to the other party inadvance, the change of setting described above with respect to theapparatus becomes easier.

Embodiment 4 Dynamic Change of Main Band and Extension Band

The characteristic features disclosed in the present Embodiment 4 willbe shown below.

i) Both of the frequency band to be occupied as the main band among aplurality of frequency bands (band 1 to band 4) and the frequency bandto be occupied as an extension band among those plurality of frequencybands can be changed along with the elapse of time without overlap, and

ii) further, one main band and at least one extension band aresimultaneously changed.

FIG. 23 is a flow chart showing an example of changing both of the mainband and an extension band.

In the present figure,

Step S71: Transmit available frequency band.

Step S72: Receive available frequency band, and

Step S73: transmit pilot channel signals using that available frequencyband.

Step S74: Receive all pilot channel signals, calculate SNRs etc., andconvert to CQIs, and

Step S75: transmit above CQIs through uplink control channel.

Step S76: Receive above CQIs,

Step S77: receive main band, that is, frequency band having bestpropagation environment,

Step S78: further, select extension band, that is, frequency band havingsecond best propagation environment,

Step S79: transmit extended frequency band and its timing of changethrough downlink control channel, and

Step S80: select timing of change thereof.

Step S81: Receive above extended frequency band and timing of change,

Step S82: change setting for each circuit unit at the timing of change,and

Step S83: start reception operation in extension band after that change.

Supplementing the explanation for the control flow of FIG. 23, here, itis assumed that each main band and each extension band are selectedbased on a predetermined transmission rate of the transmission data Du(see FIG. 24). The frequency band having the best propagationenvironment is selected as the main band based on the above CQIs of thefrequency bands transmitted from the terminal. Then, the frequency bandhaving the propagation improvement which next best to that (second) isselected as the extension band. Then, the timing of change is selected,and these are transmitted to the other party via the control channel.

The terminal receiving the used frequency band information (both of themain band and the extension band) and the change timing informationchanges the settings of the reception side circuit unit at this timingof change, then receives the two signals of the main band and theextension band.

FIG. 24 is a flow chart showing an example of the dynamic change of themain band and extension band in the present Embodiment 4 for easierunderstanding. The elapse of time goes from the top toward the bottom inthe figure. Along with that the main band is set as “BAND 1”→“BAND1”→“BAND 3”→“BAND 2” as exemplified in the present figure, the extensionband is set while forming a pair at either the left or right of the mainband (on left side or right side in the present figure). Note, the twobands do not always have to form a pair. When looking at for example thethird stage in the figure, there also exists a case where this extensionband (band 4) does not exist, and when looking at for example the fourthstage in the figure, this extension band may not exist in the shown band3, but may exist in the band 4 on the right adjacent to that with aspace.

From the above description, it becomes possible to use the frequencybands with the best and second best propagation environments as the mainband and the extension band. Further, even when the propagationenvironment changes along with time, it becomes possible to select thefrequency bands having the best and second best propagation environmentsas the main band and the extension band.

Due to this, in the same way as the above embodiments, the transmissionerror of the control channel information is reduced, the hardwaresettings on the reception side become easier, and improvement of thetransmission quality becomes possible. Further, the number of times ofresending the data can be decreased, therefore the transmission rate canbe improved. Further, by considering the processing time for correctingthe settings on the reception side and notifying the change of the mainband and the extension band to the other party in advance, the change ofthe hardware settings becomes easy.

Embodiment 5 Selection of Main Band and Extension Band According toPropagation Environment

First, the characteristic features disclosed in the present Embodiment 5are shown below.

i) Judgment of whether or not the propagation environment between thecommunications apparatuses (10, 20) is good is performed individuallyfor each of a plurality of frequency bands (band 1 to band 4), thejudgment result for each frequency band is individually transmitted tothe communications apparatus of the other party,

ii) the judgment of whether or not the propagation environment betweenthe communications apparatuses (10, 20) is good is performedindividually for each of a plurality of frequency bands (band 1 to band4), the judgment results for all frequency bands are multiplexed, andthe multiplexed results are transmitted to the communications apparatusof the other party all together, and

iii) the above judgment results are transmitted to the communicationsapparatus of the other party by using either the main band, extensionband, or frequency band having a relatively good propagationenvironment.

In carrying out the present Embodiment 5, the already explained exampleof configuration of FIGS. 15A and 15B can be used or the example ofconfiguration of FIG. 25 can be used.

FIG. 25 is a view showing an example of the hardware configuration onthe return side of the response (CQI) information to the pilot signals.The example of configuration of the present figure is similar to theexample of configuration of FIGS. 15A and 15B described above. Thedifference thereof resides in that individual processing linked witheach of a plurality of frequency bands is carried out in FIG. 15B, butin the lower half in FIG. 25, CQIs for a plurality of frequency bandsare multiplexed and processed all together. That is, in FIG. 25, thetransmission quality (CQI) is transmitted to the other party by onecontrol channel. For this purpose, a multiplexing unit (Mux) 80 isintroduced into the output side of the loop back path 77.

In the embodiments explained before, when transmitting the CQIs of thedifferent frequency bands from a terminal to the base station, they maybe transmitted through the uplink control channel for each frequencyband or the CQIs for all frequency bands may be transmitted through theuplink control channel of for example the main band.

When transmitting the CQIs by using the uplink control channel for eachfrequency band, the example of configuration of FIGS. 15A and 15B isused. Note that, in the present example of configuration, no descriptionis made of the uplink transmission data Du, but it is also possible tomultiplex this data Du on the control channel and transmit the same.Further, the present example of configuration assumes a case where pilotchannel signals are simultaneously received for a plurality of frequencybands.

In the terminal shown in FIG. 25, the signal of each frequency band isreceived and converted in frequency corresponding to that frequencyband. Thereafter, the GI is eliminated at the GI elimination unit 54, afrequency-time transform is applied by the S/P unit 55, FFT unit 56, andP/S unit 57, then the result is demodulated at the demodulation unit 23.The propagation situation is measured by the SNR, CIR, etc. using thisdemodulation signal, then the CQI value is calculated.

The above CQI value calculated for each frequency band is transmittedthrough the control channel of each frequency band. At this time, it isalso possible to transmit the other control channel signal together.Further, it is also possible to transmit the same together with theuplink transmission data.

The calculated CQI enters into the part of FIG. 15B by the loop backpath 77, is encoded at the encoding unit 78, modulated at a modulationunit 112, then subjected to a time-frequency transform at an S/P unit137, an IFFT unit 138, and a P/S unit 139. Further, the GI is insertedat a GI insertion unit 140, then the result is converted to thecorresponding frequency band and transmitted from the antenna AT.

From the above description, it becomes possible to transmit the CQI(propagation situation) of each frequency band to the base station inthe same way as the embodiments explained before. Further, it becomespossible to select the frequency band having a good propagationenvironment as the main band based on the CQIs (propagation situations)sent from the terminal. In the same way, it becomes possible to selectthe frequency band having a relatively good propagation environment asthe extension band. In this way, in the same way as the embodimentsexplained before, the transmission characteristics are improved by usingthe better frequency band, and the number of times of resending the datais decreased, therefore improvement of the transmission rate becomespossible.

Next, the example of configuration of FIG. 25 described above isemployed for a case of transmitting all CQIs by using the uplink controlchannel of a specific frequency band. In the same way as the case ofusing the uplink control channel for each frequency band explainedabove, the CQI in each frequency band is calculated. These calculationresults are combined into one at the above multiplexing unit (Mux) 80,then this is encoded at the encoding unit 78. Further, it is modulatedat the modulation unit 112, then subjected to a time-frequency transformat the S/P unit 137, IFFT unit 138, and P/S unit 139 and given a GI atthe GI insertion unit 140. Thereafter, the result is converted infrequency by the circuits 141 and 142 and transmitted from the antennaAT.

Note that, as the frequency band used for the transmission of the CQI tobe used, the main band which is selected because of its relatively goodtransmission environment may be selected, the frequency band having thebest propagation environment (best CQI) may be selected, and anotherfrequency band may be selected. Further, the frequency band previouslyset as the communications system may be used.

From the above description, in the same way as the embodiments explainedbefore, it becomes possible to transmit the CQI (propagation situation)of each frequency band to the base station. Further, it becomes possibleto select the frequency band having a good propagation environment asthe main band based on the CQI (propagation situation) sent from theterminal. In the same way, it becomes possible to select the frequencyband having a good propagation environment as the extension band. Byselecting the better frequency band in this way, the transmissioncharacteristics are improved, the number of times of resending the datais decreased, and therefore improvement of the transmission rate becomespossible.

Embodiment 6 High Efficiency Transmission of Used Frequency BandInformation

The characteristic feature disclosed in the present Embodiment 6 isthat, for each of a plurality of frequency bands (band 1 to band 4), atleast one of information (i to iv) of (i) a frequency bandidentification number, (ii) used/not yet used as main band, (iii)used/not yet used as extension band, and (iv) current status maintainedis encoded and transmitted to the communications apparatus of the otherparty.

FIG. 26 is a view showing tables for explaining the high efficiencytransmission of the used frequency band information. Table 1 shows anexample of correspondence of the used frequency band and band number,and Table 2 and Table 3 show a first example and a second example of themethod of setting of used/not yet used of the used frequency band.

In the transmission of the above used frequency band information in theembodiments explained above, for example, by assigning numbers tofrequency bands and transmitting the numbers, the amount of controlchannel information can be reduced in comparison with the case where thevalue of frequency per se is transmitted. A concrete example will beexplained by using the above Table 1 to Table 3. Note that, here, anexample where the frequency band useable by the communications system asa whole is set to 800 MHz to 820 MHz and this is divided into fourfrequency bands as in FIG. 9 for use is shown.

First, band numbers (1, 2, 3, 4) are assigned to the bands as shown inTable 1. Further, which frequency band is to be used as the main band,and which frequency band is to be used (or not used) as the extensionband is set as in Table 2.

At this time, in for example a case where the band 1 is “not yet used”,the band 2 is used as the “main band”, the band 3 is used as the“extension band”, and the band 4 is “not yet used”, the followingcontrol data “yy1100zz” is obtained wherein yy and zz are “01” or “10”.

Note that, here, the above control data was prepared in a sequence ofband 1, band 2, band 3, and band 4, but this sequence may be any so faras recognition is possible on the transmission side and the receptionside. Further, the number of bands can be freely increased or decreased.Further, an explanation was given here by taking as an example fourconsecutive frequency bands, but nonconsecutive frequency bands havingnot yet used bands in the middle may also be employed.

As described above, by encoding information (forming tables), the amountof information can be reduced in comparison with for example the casewhere the value of the center frequency of the band per is transmitted.

Further, as shown in Table 3, it is also possible to provide settings inthe case where there is no change in the usage situation, that is, thecase of “current status maintained”.

By encoding (forming tables) the used frequency band information asdescribed above, the data length of the control signal can becompressed. Accordingly, the ratio of the transmission data and thecontrol channel information is reduced for the latter, and accordinglythe transmission efficiency of the transmission data is improved.

Embodiment 7 Continuous Setting and Nonconsecutive Setting of ExtensionBands

First, when describing the characteristic features disclosed in thepresent Embodiment 7, they are as follows.

i) One extension band or two or more consecutive extension bands areassigned as the frequency bands consecutive to the main band on thefrequency axis,

ii) or an isolated extension band not consecutive with any of theextension bands is further included on the above frequency axis, and

iii) a signal having no meaning is inserted in the not yet usedfrequency band accompanying the above isolated extension band andtransmitted to the communications apparatus of the other party. Notethat as views representing the present Embodiment 7, there are FIG. 27and the already explained FIG. 22.

FIG. 27 is a view showing an example of dynamic change of the extensionband. In contrast to the above FIG. 22 showing the case whereconsecutive extension bands are selected, FIG. 27 shows a casenonconsecutive extension bands (see the fourth stage of the samediagram) are selected. Note that the method of viewing FIG. 27 isexactly the same as the method of viewing the above FIG. 22. This willbe concretely explained below.

First explaining the case where the extension bands are consecutive, thealready explained FIG. 22 shows a case where the extension bands areconsecutively selected. Note as one example, a case where a consecutiveband forming a pair with the main band is selected as the extensionband. In the mode of this FIG. 22, the extension band is consecutivewith the main band, therefore, in comparison with the case ofnonconsecutive bands (FIG. 27), the signal processing becomes simpler.Note that the transmission operation and the reception operation are thesame as those explained in the above embodiments.

On the other hand, FIG. 27, as described above, also shows a case wherean extension band is nonconsecutive (fourth stage). In this way, it isalso possible to nonconsecutively select an extension band with respectto the main band or an adjacent extension band from the used frequencyband of the terminal, the propagation environment, and the balance withother terminals.

Note that a subcarrier bridging the consecutive frequency bands (see adotted line SC of FIG. 22) is not set in the explanation hitherto, butaccording to the usage situation of the other terminals, it is alsopossible to set a subcarrier bridging two frequency bands and increasethe amount of transmission information by that amount.

Further, the reception side terminal does not receive signals at theabove nonconsecutive frequency bands or forcibly processes the relatedsignals as meaningless signals. Due to this, even when the extensionbands are non consecutive, reception can be carried out without problem.

As described above, by setting nonconsecutive extension bands, itbecomes possible to flexibly select the extension bands considering theused frequency band of the terminal, the propagation environment, andthe usage situation of the other terminals. Further, due to this, theefficiency of frequency utilization is further improved.

Embodiment 8 Making Number of Subcarriers in Each Frequency BandConstant

The characteristic feature disclosed in the present Embodiment 8 residesin that the bandwidth of each of a plurality of frequency bands (band 1to band 4) is set to a predetermined constant value and the number ofthe series of subcarriers in each band is made a predetermined constantvalue.

FIG. 28 is a view showing a first example of a band extension pattern,FIG. 29 is a view showing a second example of a band extension pattern,and FIG. 30 is a view showing a third example of a band extensionpattern.

Note that the method of viewing these FIG. 28 to FIG. 30 issubstantially the same as the method of viewing the above FIG. 22, FIG.24, FIG. 27, etc. While FIG. 22, FIG. 24, FIG. 27, etc. show patternsusing actual waveforms, FIG. 28 to FIG. 30 only show patterns as blocksof subcarriers in place of such actual waveforms. This is forfacilitating the explanation of the present Embodiment 8. Namely, theyshow the concept of a “frequency band unit” visually for easierunderstanding. Note that terms described in FIG. 28 to FIG. 30 arealready explained except a “processing delay”. This processing delay,when viewing for example FIG. 4, means a time delay required for theprocessing from when the used frequency band information If is input tothe used frequency band setting unit 25 to when the band set instructionsignal Sb is generated and further the parameters finish being set ineach circuit part.

In general, in the multicarrier transmission mode (OFDM, MC-CDMA etc.)or other communication system using a series of subcarriers, whenchanging the bandwidth, ordinarily the change is carried out in units ofsubcarriers. In this case, used/not yet used must be set in unit ofsubcarriers. Further, in the sending processing and receivingprocessing, signal processing considering “used/not yet used” in unit ofsubcarriers is necessary, so the setting of bands is liable to becometroublesome and complex. Further, in a case where the users aremultiplexed, control of used/not yet used of each subcarrier isnecessary between users. As a result, a drop in the efficiency offrequency utilization is caused.

Therefore, in the present Embodiment 8, the used frequency band of thecommunications system as a whole is divided into a plurality of bands(band 1 to band 4), the “number of subcarriers is made constant” in thedivided frequency bands, and transmission between communicationsapparatuses is carried out by using one or more of the frequency bands.Due to this, an improvement of the efficiency of frequency utilizationcan be achieved.

Specifically, for example one frequency band is set to 5 MHz, and thenumber of subcarriers in that frequency band is set to 25. By setting aplurality of such frequency bands, the above used frequency band is madevariable in units of frequency bands. The above FIG. 28 to FIG. 30 showconcrete examples of band extension in units of bands. An abscissa ineach diagram indicates the bandwidth, one hatched block represents onefrequency band, and a plurality of subcarriers are assumed to becontained in that one frequency band. In the same way as FIG. 9, it maybe considered that the band 1, band 2, band 3, and band 4 are arrangedfrom the left.

FIG. 28 shows a case where the band 1 is used as the main band, and FIG.29 shows a case where the band 2 is used as the main band. Further, FIG.30 shows an example of changing the setting of the extension band alongwith the elapse of time and shows a case where those extension bandsinclude a nonconsecutive one (see the sixth stage). Note that theconcrete operation of transmission/reception is as explained in theabove embodiments.

From the above description, the used frequency band can be easily madevariable, and it becomes possible to raise the utilization efficiency ofthe frequency. Further, when compared with the case where the usedfrequency band is made variable in units of subcarriers, the abovetransmission/reception operation becomes further simpler, and theconfiguration of a transmitter/receiver becomes simpler.

Embodiment 9 Making Both Number of Subcarriers and Subcarrier Bandwidthin Each Frequency Band Constant

Describing characteristic features disclosed in the present Embodiment9, they are as follows:

i) The bandwidth of each of the plurality of frequency bands (band 1 toband 4) is made a predetermined constant value, and the bandwidth ofeach subcarrier in each band is made a predetermined constant value, and

ii) further, also the number of subcarriers is made a predeterminedconstant value. Due to this, the main band and the extension band can beeasily set in units of frequency bands.

In the above Embodiment 8, the number of subcarriers per band was madeconstant, but in the present Embodiment 9, the bandwidth of eachsubcarrier is also made constant.

As a result of this, the difference between bands becomes only thecenter frequency of each. Due to this, baseband signal processing ismade uniform irrespective of the frequency band, and, when compared withEmbodiment 8, the configuration of the transmitter/receiver becomesfurther simpler.

Embodiment 10 Setting of Band Based on Difference Between PredeterminedTransmission Rate and Real Transmission Rate

Describing the characteristic features disclosed in the presentEmbodiment 10, they are as follows:

i) In order to judge necessity/unnecessity of an extension band, thedifference between a predetermined transmission rate S1 assumed to benecessary for the exchange of information and an actual transmissionrate S2 which is actually achieved (S1−S2) is calculated. It is judgedwhether the extension band is required or not required in accordancewith the positive or negative sign of this difference, and

ii) here, the above actual transmission rate is found from the number ofthe transmission data information calculated from the number of usedfrequency bands and the transmission interval of the transmission datainformation.

FIG. 31 is a view showing an example of the configuration of thecommunications apparatus (transmission side) according to Embodiment 10,and FIG. 32 is a flow chart showing an example of the operation in theapparatus of FIG. 31.

Referring to FIG. 31 first, the figure is substantially the same as theconfiguration of the above FIG. 5 (also FIG. 3 is the same), but differsin the point that a frequency band selecting/setting unit 85(modification of 15) and an actual transmission rate calculation unit 86shown on the left end in the figure are introduced.

Further, referring to FIG. 32, the operation thereof is:

Step S91: Confirm predetermined transmission rate,

Step S92: confirm amount of transmission data, and

Step S93: calculate actual transmission rate.

Step S994: Judge whether or not it is necessary to extend used frequencyband based on rate values in steps S91 and S93 and judge that it isnecessary.

Step S95: Select extended frequency band and determine timing of change,and

Step S96: transmit that extended frequency band and its timing of changethrough downlink control channel.

Step S97: Receive extended frequency band and timing of change,

Step S98: change setting of each circuit unit at that timing of change,and

Step S99: start reception by using extension band after change.

Explaining this further concretely, in the above Embodiment 1, used/notyet used of the extension band and the number of extension bands weredetermined based on only the predetermined transmission rate, but in thepresent Embodiment 8, the extension or reduction of the band is carriedout by considering the difference between the actual transmission rateand the predetermined transmission rate.

A concrete example will be explained by using FIG. 31 and FIG. 32 again.Note that the explanation will be omitted for the same parts as those inEmbodiment 1.

Assume that a predetermined transmission rate Rd of a certaintransmission data Du is 10 Mbps, and the transmission is carried out byusing the main band and the extension band. At this time, from thenumber of transmission data calculated from the number of used frequencybands and the transmission interval thereof, an actual transmission rateRa can be calculated by an actual transmission rate calculation unit 86of FIG. 31. This actual transmission rate Ra and the predeterminedtransmission rate Rd are compared at the above selecting/setting unit85. When the actual transmission rate Ra is lower, the used frequencyband is increased (extended). Further, for example, when is judged thatthe predetermined transmission rate Rd can be secured even when theactual transmission rate Ra is much higher than the predeterminedtransmission rate Rd and the used frequency band is decreased, the usedfrequency band is decreased (reduced).

From the above description, an improvement of the efficiency offrequency utilization can be achieved while satisfying the predeterminedtransmission rate. Note that, other than the above method, it is alsopossible to ask the base station to return whether or not the datatransmitted from the base station could be transmitted to the terminal(ACK/NACK), calculate the actual transmission rate based on that, andmake the used frequency band variable. Further, it is also possible tocalculate the transmission rate based on the amount of data transmittedfrom the base station to the terminal, ask the terminal to return thistransmission rate value to the base station, and make the used frequencyband variable based on that value.

Embodiment 11 Enlargement of Used Frequency Band

FIG. 33 is a view for explaining the present Embodiment 11. The parts tobe particularly noted are a “restricted band” and a “overall frequencyband after lifting restriction”. Here, the characteristic featuresdisclosed in the present Embodiment 11 are as described below:

i) In a communications system for exchange of information betweencommunications apparatuses (10, 20) by the multicarrier transmissionmode using a series of subcarriers, in a case where the usage of only apart of the divided frequency bands (“band a”) is permitted at presentamong a plurality of divided frequency bands (band a to band d) formedby dividing the overall frequency band to be assigned to thiscommunications system in the future (see “overall frequency band afterlifting restriction” of FIG. 33) (see “restricted band”), that dividedfrequency band “band a” allowed to be used is operated further dividedinto one or more frequency bands (like band 1 to band 4 in Embodiments 1to 10). At the same time, each of the other divided frequency bandswhich are restricted at present (band b, band c, and band d) is dividedinto one or more frequency bands in the same way as the former (likeband 1 to band 4 in Embodiments 1 to 10) in advance. Then, when therestriction is lifted in the future, each of the plurality of dividedfrequency bands (band b to band d) which are formed by dividing theoverall frequency band but not yet used at present is immediatelyoperated by the same operation as the operation of dividing the dividedfrequency band (band a) allowed to be used at present into one or morefrequency bands, and

ii) here, the plurality of frequency bands (band a to band d) formed bydividing the overall frequency band have constant bandwidths withrespect to each other, and the number and bandwidth of subcarriers ineach of those divided frequency bands have constant values with respectto each other.

Explaining this further concretely, there may be cases where frequencyband usable by the present communications system (or base station) isrestricted from the balance with other communications system but laterthe restriction is lifted for a reason that the frequency used by theother communications system is shifted elsewhere and so on.

When assuming such case, the above limited used frequency band (“limitedband a”) is operated by dividing the band (a) into one or more frequencybands in the same way as the above embodiments. Then, at this time, therestricted frequency bands (band b, band c, and band d) are individuallydivided to one or more frequency bands as well. Note that preferably theused frequency band (band a) and restricted frequency bands (bands b tod) are divided with the same bandwidth. FIG. 33 assumes division withthe same bandwidth in this way. Further, in FIG. 33, the used frequencyband is limited to the “band a” which is operated as a single frequencyband. The whole restricted frequency band is divided into three bands(band b to band d), but these bands b to d can not be used at presentdue to the restrictions. Note that the number of subcarriers and thesubcarrier bandwidth of each of these bands are constant.

Note that, while restricted, the frequency band is set as a single band(band a), therefore the used frequency band cannot be extended.According to the present Embodiment 11, after the lifting of therestriction described above, the number of used frequency bands becomesfour (bands a to d), and the operation can be immediately shift to theoperation of the embodiments explained before.

By setting the frequency band as described above, the used frequencyband is limited at present, but when the restriction is lifted afterthat, the operation can be immediately shifted to the system operationaccording to the present invention. This enables the flexible operationof the communications system.

As explained in detail above, according to the present invention, itbecomes possible to easily make the used frequency bandwidth variable,and due to this, the utilization efficiency of the frequency can be muchenhanced.

What is claimed is:
 1. A base station accommodated in a communications system for communicating with a mobile station, the base station comprising: a transmitter configured to generate frequency band information indicating which frequency band of frequency bands used in the communications system to communicate with a mobile station, to transmit the frequency band information by using a specific frequency band selected from a plurality of frequency bands available in the communications system, and to communicate with the mobile station using at least one of the plurality of frequency bands.
 2. The base station as set forth in claim 1, wherein, at least one of information of a frequency band identification number and used/not used state, as at least one frequency band, is transmitted to the mobile station, for each of said frequency bands.
 3. The base station as set forth in claim 1, wherein the frequency bands except for the specific frequency band, are made variable.
 4. A mobile station accommodated in a communications system for communicating with a base station, the mobile station comprising: a receiver configured to receive frequency band information indicating which frequency of frequency bands used in the communications system to communicate with the base station, using a specific frequency band selected from a plurality of frequency bands available in the communications system, and to receive information by one or more frequency bands based on the frequency band information.
 5. The mobile station as set forth in claim 4, wherein, at least one of information of a frequency band identification number and used/not used state, as at least one frequency band, is received from the base station, for each of said frequency bands.
 6. The mobile station as set forth in claim 5, wherein, said at least one frequency band is set from the frequency bands except for the specific frequency band. 